Stair climbing wheel chair



Aug. 14, 1962 E. o. CLAY 3,049,364

STAIR CLIMBING WHEEL CHAIR Filed April '7, 1961 6 Sheets-Sheet 1 INVENTOR. EUGENE O. CLAY ATTORNEY Aug. 14, 1962 E. 0-. CLAY 3,049,364

STAIR CLIMBING WHEEL CHAIR Filed April 7, 1961 6 Sheets-Sheet 2 e4 I I 2| 82 E 79 I 1 I I6 74 7o H IIHIII IN V EN TOR.

EUGENE O. CLAY ATTORNEY Aug. 14, 1962. E. o. CLAY STAIR CLIMBING WHEEL CHAIR 6 Sheets-Sheet 3 Filed April 7, 1961 INVENTOR.

ATTORNEY Aug. 14, 1962 E. o. CLAY 3,049,364

STAIR CLIMBING WHEEL CHAIR Filed April 7, 1961 6 Sheets-Sheet 4 FIG.4

INVEN TOR.

EUGENE O. CLAY I5 37 BY ATTORNEY Aug. 14, 1962 E. o. CLAY 3,049,364

STAIR CLIMBING WHEEL CHAIR Filed April 7, 1961 6 Sheets-Sheet 5 INVENTOR. EUGENE O. CLAY ATTORNEY Aug. 14, 1962 E. o. CLAY 3,049,364

STAIR CLIMBING WHEEL CHAIR Filed April 7, 1961 6 Sheets-Sheet 6 IN V EN TOR. EUGENE O. CLAY ATTORNEY 3,049,364 STAIR CLHVIBING WHEEL CHAIR Eugene 0. Clay, 3717 Floresta Way, Los Angeles, Calif. Filed Apr. 7, 1961, Ser. No. 101,412 laims. (Cl. 280-211) This invention pertains to a Wheel chair capable of negotiating stairs or the like when operated solely by the occupant of the chair.

There has existed an obvious need to provide a wheel chair having the ability to climb stairs or travel over other obstructions. A conventional wheel chair cannot contend with even a small obstruction in its path, and must in effect be lifted up the stairs by an attendant. Hence, unless there has been provided a ramp or an elevator, it is impossible for a wheel chair operated by the occupant to negotiate the obstructions commonly encountered in traveling about. This has meant that for patients confined to a wheel chair, many areas are inaccessible due to the impracticality of continual attendance of an additional person to lift the chair and occupant over obstructions.

There have been various proposals in the past to mitigate the problem, but none of these has actually eliminated the difiiculty. Such designs have included pivotal arms that support the ground-engaging wheels so that when stairs are encountered the arms rather than the wheels may be rotated in enabling the chair to be brought up the stairs. In all instances, however, this has necessitated the presence of an attendant to move the chair up or down the steps and has not provided a unit operable solely by the occupant. Thus, although the problem has been made easier in some respects for the attendant, the necessity for the services of a second person has not been eliminated.

According to the provisions of this invention a wheel chair is provided that is capable of climbing or descending stairs, curbs or similar obstructions through the operation of the occupant of the chair. In accomplishing this, the chair unit is supported on a plurality of trucks, each of which is provided with two wheels, all of the wheels being drivingly interconnected. The trucks, in turn, are pivoted to a movable frame that supports the chair. The connection of the trucks to the frame includes suitable pivotal links that permit the drive train to be shortened longitudinally as the stairs are being negotiated. The seat for the occupant is rotatable relative to the movable frame so that it remains in an upright position at all times. In addition, an automatically engageable brake is included that locks the drive unit whenever the operating force is released. This brake may be disengaged to permit conventional operation by pushing the wheel chair in the usual manner.

Therefore, it is an object of this invention to provide a Wheel chair capable of negotiating stairs or the like.

Another object of this invention is to provide a wheel chair movable by the occupant or an attendant as a conventional wheel chair on a flat surface, while being operable by the occupant for climbing up or down stairs or other obstructions.

A further object of this invention is to provide a wheel chair capable of negotiating stairs or the like that is provided with an automatic brake engageable whenever the driving force is released.

An additional object of this invention is to provide a stair-climbing wheel chair having an automatic brake, which brake can be disengaged for operation by pushing the chair in the conventional manner.

Yet another object of this invention is to provide a stair-climbing wheel chair in which the occupants seat remains in an upright position at all times.

fi l fifi i Patented Aug. 14, 1962 A still further object of this invention is to provide a stair-climbing wheel chair of simplified construction that is safely and easily operated by the occupant of the chair.

An additional object of this invention is to provide a wheel chair that negotiates obstructions by forward motion for both ascent and descent.

These and other objects will become apparent from the following detailed description taken in connection with the accompanying drawing in which:

FIG. 1 is a side elevational view of the wheel chair of this invention operating on a level surface,

FIG. 2 is an enlarged fragmentary end elevational view, taken from the rear, of one side portion of the wheel chair,

FIG. 3 is an enlarged fragmentary side elevational view illustrating the support frame and running gear,

FIG. 4 is an enlarged sectional view taken along line 44 of FIG. 3 showing the connection of the intermediate trucks to the frame,

FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 3 illustrating the connection of the rear truck to the support frame, the arrangement of the guide plate for maintaining the equilibrium of the chair unit, and the power input to the wheels,

FIG. 6 is a fragmentary plan view taken along line 6-6 of FIG. 3 further illustrating the power input to the drive train,

FIG. 7 is an enlarged axial sectional view of the automatic brake and the connection of the hand wheel to the main drive socket.

FIG. 8 is a transverse sectional view taken along line 88 of FIG. 7,

FIG. 9 is an enlarged fragmentary sectional view showing the brake in the locked position with the released position indicated in phantom,

FIG. 10 is a side elevational view of the wheel chair similar to FIG. 1 but illustrating the unit climbing a stairway, and

FIG. 11 is a side elevational View similar to FIGS. 1 and 10 but with the wheel chair descending a stairway.

The wheel chair of this invention is symmetrical so that in most instances only the construction of one side of the unit is illustrated and described herein. It includes a chair unit 1, a movable frame support unit 2, and a drive train 3. The chair unit may be conventional to the extent that it includes a seat 4 and back 5, as well as handles 6 for customary operation by the pushing of an attendant.

A pair of trammels or side members 7, each made up of two closely spaced parallel plates, is provided for supporting the chair on the movable frame 2. The chair unit is pivotally connected to the trammels by the provision of brackets 8 suitably secured to each arm portion '9 of the frame of the chair unit. A pin 10 pivotally connects each trammel to the bracket and in turn, therefore, to the frame of the chair. These pivot pins 10 are located above the center of gravity of the chair unit when the occupant 12 is seated in the chair along a transverse vertical plane 11 that intersects the center of gravity. Thus, although the chair assembly 1 is capable of rotating about the transverse aris formed by pivot pins 10, there is no tendency for such rotation during normal occupany of the chair while the unit is on a level surface as illustrated in FIG. 1.

Each side of the movable support frame 2 is of tubular construction including an arcuate upper portion 14-, and a bifurcated lower section 15. If desired, a web 16 may be included on the lower edge of the upper portion '14 to give the unit added rigidity. Preferably, lightening holes 17 perforate the web to reduce the weight of the unit.

As best seen in FIG. 2 the trammels 7 support the chair unit on the movable frame 2 through hourglass rollers 18 and 19 located on either side of line 11. Additional arcuate rollers 20 and 21 preclude movement vertically of the chair unit relative to the support frame. This means that the bottom portions of the trammels are movable along the upper portions 14 of the two sides of the movable frame assembly along the are of the radius generating this upper portion 14. The trammels 7 act as suspension members in that they provide a suspension means to suspend the chair on the frame.

Any tendency for the chair unit 1 to pivot from its upright position is precluded by means of a pair of guide units 23. These guides are in the form of plates that are secured to the bottom rails 24 of the chair unit, and include vertical slots 25. These slots slidably receive pins 26 that are carried by the lower bifurcated portion 15 of the movable support frame 2. The slots 25 and pins 26 fall along the vertical line 11 that passes through the center of gravity of the chair when occupied. Also, the pins 26 are positioned substantially at the center point for the radius of curvature of the upper frame portion 14.

The drive train 3 includes on either side of the wheel chair of this invention four trucks 28, 29, 30 and 31. Each truck includes a pair of generally triangular shaped parallel side plates 33 which through axles 34 rotatably connect to wheels 35. Thus, each truck is provided with two wheels which preferably have rubber tires and are much smaller than the conventional wheels utilized in supporting a wheel chair.

The rear trucks 28 have fixed pivotal connections to the lower portion 15 of the support frame 2 through pins 37. These pins extend through both branches of the bifurcated portion 15 of the frame and engage the top of the plates 33 of the rear trucks 28.

Each of the front trucks 31 extends slightly forward of the support frame 2 to which it is connected by means of a rearwardly inclined link 38. This link is pivotal relative both to the front truck and the support frame by reason of its connection to these elements through transverse pins 39 and 40.

Extending from the top of the side plates 33 of the two central trucks 29 and 30 are links 41 and 42 which are pivotal relative to the trucks through pin connections 43 and 44. For convenience in manufacture and assembly, each of these links may be made from a pair of identical parallel elements, as seen for the link 42 in FIG. 4. The opposite ends of the links 41 and 42, by pivot pins 45 and 46, are joined to a longitudinally extending walking beam 47. The latter element at its center is connected by transverse pivot pin 48 to the lower portion 15 of the support frame 2.

The motive power for each drive train is introduced through a chain drive that includes a sprocket 50 carried by transverse pivot pin 37 of the rear truck 28, as best seen in FIGS. 2 and 5. The sprocket 50 is rotated by the shaft 37, as will be more clear hereinafter. A roller chain 51 engages the sprocket 50 and likewise meshes with a sprocket 52 on the axle 34 of the rear wheel 35:: of the rear truck 28. The sprocket 52 is rotatably coupled to the rear wheel 35a and located on one side of the wheel as illustrated. Thus when sprocket 50 turns, the chain 51 and sprocket 52 cause rotation of the rear wheel 35a of the rear truck 28.

A similar sprocket 53 is positioned on the opposite side of the rear wheel 350, also being rotatably connected to this Wheel. A chain 54 meshes with the sprocket 53 and also with a sprocket 55 of equal diameter immediately forward of it on the axle 34b of the wheel 35b of the rear truck 28. The sprocket 55 is rotatably fixed with respect to wheel 3512 so that rotation of this sprocket drives the wheel 35b.

Also rotatably coupled to the wheel 35b is an additional sprocket 56 which meshes with a chain 57 similar to the chain 54. The chain 57 extends to a sprocket connected to rear wheel 350 of the truck 29 so that the chain 57 can provide a driving force to the wheel 350.

Except for the front wheel of truck 31, each of the wheels in the drive train is connected to a duality of sprockets, similar to sprockets 52 and 53 and sprockets 55 and 56. The front wheel of the train needs only one such sprocket, having no wheel ahead of it. Chains 58, 59, 60, 61 and 62 interconnect these sprockets so that a driv ing connection is provided for all of the wheels in the power train. In this manner a torque applied to the rear wheel 35a is transmitted throughout the chain drive system to each of the wheels. Therefore, power is supplied to all of the wheels in the drive train, and all of the wheels in either drive train rotate together and at equal speeds.

The trucks are maintained in a spaced relationship with each other through the provisions of links 64, 65 and 66 which pivotally engage axles 34 of the trucks. Therefore, although the wheels are all driven equally and Simultaneously, the chain drive connections and the spacing links 64, 65 and 66 permit the trucks to be pivoted relative to each other.

In the embodiment illustrated, the wheel chair is manually operated through a pair of large drive wheels 68, the rims of which may be grasped by the occupant of the wheel chair and rotated to supply the driving force. it is obvious that other types of drive arrangements could be provided, if so desired, providing rotation through an electric motor, gasoline engine, or any suitable prime mover.

Each drive wheel 68 includes at its axis a hub 69 projecting inwardly toward the chair (see FIG. 7). Each hub 69 is in the form of a cylindrical tubular element rotatably carried by the inner race of antifriction bearing 70. The outer race of this hearing is supported in the end wall 71 of a cup-shaped member 72. The latter member is in turn carried by the movable support frame 2, connecting at its edges to upper portion 14 of the frame and to the web 16. The web 16 also carries the outer race of antifriction bearing 74, which is spaced from and coaxial with the bearing 70. The inner race of bearing 74 supports a stub shaft 75 which extends also into the tubular hub 69. Stub shaft 75 is axially slidable relative to both the bearing 74 and the hub 69.

Integral with the stub shaft 75 is the main drive sprocket 76. This sprocket meshes with a roller chain 77 that extends downwardly to engage a smaller sprocket 78 on the pin 37 for causing rotation of this sprocket, and thus of the sprocket 50 that connects to the drive train.

An automatic brake is provided in the connection between the power input wheel 68 and the main drive sprocket 76. To this end, the hub 69 includes a radial plate 79 to which is fixed a duality of receptacles 80 and 81 which may include short cylindrical sections projecting axially from the radial plate 79. The receptacles 80 and 31 contain balls 82 and 83 which are rotatable relative to the receptacles and project outwardly therefrom. Opposite the balls 82 and 83, the sprocket 76 is provided with circular apertures 84 and 85. These openings are slightly smaller in diameter than the diameter of the balls 82 and 83. Nevertheless, the balls may extend into the openings 84 and 85 sufi'iciently to permit the sprocket 76 to assume the position illustrated in FIG. 9 in which the periphery of the sprocket and the chain are brought into engagement with annular member 87 extending around the interior of the cup'shaped member 72. The sprocket 76 is biased to this position by means of spring 88 which bears upon the inner race of bearing 74 and the inner portion of the sprocket. The annular member 87 is of a material having a high coefficient of friction, and may be formed from an element of rubber composition such as an ordinary drive belt. It is apparent, therefore, that with the sprocket in engagement with the annular member 87 as a result of the force of spring 88, the sprocket and main drive chain 77 will be frictionally gripped by braking member 87 and precluded from rotation. The uneven side surface presented by the drive chain 77 enables it to dig into member 87 and enhances the frictional resisting force. The result is a brake that locks all of the wheels 35 through the chain 77, chain 51 and the chains in the drive train interconnecting the wheels.

When it is desired to operate the wheel chair, the hand wheel 69 is rotated by the occupant. As this occurs the plate 79 is turned relative to sprocket 76 so that balls 82 and 83 tend to climb out of the openings 84 and 85. Such movement of the balls 82 and 33 can be accomplished only by axial displacement of the sprocket 76 relative to radial plate 79. Therefore, as the balls are rotated by plate 79, they exert an axial force urging the sprocket 76 to the left of the position shown in FIG. 9 to assume the position of FIG. 7. This shifts the sprocket 76 axially away from the annular braking member 87 so that it no longer is locked against movement. Thus, rotation of the wheel 68 automatically releases the brake on the running gear. Due to the relatively small penetration of the balls into the openings 84 and 85 when the sprocket 76 is in its normal position against the braking element 87, a large mechanical advantage is realized in effecting the brake release.

As illustrated in FIG. 8, blocks 90 and 91 are located inrmedately forward of the openings 84 and 85 about a circumference that includes the centers of these Openings. These blocks act as stops limiting the amount of movement of the radial plate 79 relative to the drive sprocket 7 6. in other words, the hand wheel 68 is rotated only a very slight amount relative to the drive sprocket 76 until the receptacles 8i and 81 are brought into contact with the stops 9% and 91. This results in a driving connection between the hand wheel and the drive sprocket. Continued rotation of the hand wheel 68, therefore, rotates the drive sprocket which in turn drives the chains causing the wheels 35 to turn in the same direction as the hand wheel.

Of course in order to allow reverse movement as well as forward, additional blocks 92 and 93 are provided on the opposite sides of openings 84 and 85. Hence, relative movement between the hand wheel and the drive sprocket in the opposite direction likewise disengages the brake and effects a driving connection.

It is apparent from the foregoing, therefore, that the drive unit of this invention includes a brake that automatically is applied when the hand wheel 63 is released. This permits the spring 88 to force the drive sprocket into engagement with the annular braking element 87, and brings the balls 82 and 83 to the innermost position within the openings 84 and 85. Nevertheless, upon rotation of the hand wheel in either direction, the brake is released and the wheels of the drive train are turned.

in order that the wheel chair unit of this invention may be pushed by hand by an attendant in the conventional manner, or to all-ow it to coast on a level surface, an arrangement is included to disengage the brake so as to render it inoperative. This is effected very simply through release screws 95 each of which includes an enlarged head as for convenient rotation, and a threaded shank 97 on gaging a tapped opening through the axis of the hand wheel 68. When it is desired to release the brake, it is necessary only to rotate the screws 95 so as to move them inwardly, causing the ends of shanks 97 to contact the ends of stub shafts 75. These shafts then are moved axially in opposition to the opposing force of springs 38, to shift sprockets 76 away from the braking members 87. Of course reverse movement of the screws 95 again renders the brake operative.

As a result of the above-described arrangement, it is apparent that the wheel chair of this invention may be operated in the conventional manner on a level surface, as indicated generally in FIG. 1. This can be by manipulation of hand wheel 68 by the occupant of the wheel chair, or alternatively from the provision of a prime mover as the source of power. In addition, with release of the brake an attendant may push the wheel chair by the handles 6.

Also however, this design allows the wheel chair to climb up or down a stairway or other obstruction entirely through the operation of the occupant of the wheel chair, as seen in FIGS. 10 and ll. In order to negotiate stairs or other obstructionss the wheel chair is merely driven forwardly to bring the front wheels 35 of the front trucks 31 into engagement with the vertical riser 98 of the bottom step of the stairway. Continued rotation of the hand wheels 68 will cause these front wheels to climb up the riser 98 to reach the level of the tread as of the next step. This occurs because the front wheels 35 are power driven and will tend to move up the riser due to the friction generated between the surface of the wheel and that of the riser. In addition they are forced to climb due to the power applied forwardly from the additional wheels supporting the weight of the unit on level surfaces. The movement upwardly of the front wheels 35 is permitted by the pivotal connection of the front trucks 31 to the movable support frame through the links 38, as well as the pivotal connection between trucks 3% and 31 through spacer links 65.

When the front trucks 31 have reached the level of the tread of the first step in a stairway, the second trucks by that time will be climbing the riser in a similar man ner. The pivotal connections of the second truck through the links 12 and the walking beams 47 allow these trucks to swivel and to negotiate the step.

The trucks successively climb up the first step and the succeeding steps of the stairway and may achieve the position shown in FIG. 10 where the entire unit is on the stairs. in this manner, the wheels on their pivotal trucks cause the wheel chair to climb up the stairs regardless of the number of steps encountered or the steepness of the stairs. It may be noted that during the negotiation of the stairs, there are always some Wheels on the level surfaces of the treads, while others may be clim ing up the vertical risers of the stairs. For example, in the position of the wheel chair in FIG. 10, both wheels of the front trucks 31 are on a level surf-ace, as are both wheels of the rear trucks 28, the front wheel of the trucks 29 and the rear wheel of the trucks 3% The wheels on the level surface provide the unit with the necessary stability and support its weight, as well as giving a forward driving force to cause the Wheels to work their way up the stairs.

The connection of the two middle trucks 2.9 and 30' on either side to the frame through walking beams 47 enhances the action of the unit considerably as it negotiates the stairs. 'It allows a vertical shifting of the pivotal connections of these trucks relative to support frame 2-, and permits the wheels of these trucks to maintain contact with the stair steps as the wheel chair advances. In this manner, all of the wheels are used in supporting the weight of the unit and maintaining its equilibrium. Connection of the center trucks separately through straight links such as the links 38 for the front trucks 31 would not give this result.

As an essential part of the stair climbing ability of the wheel chair of this invention, the movable support frame 2 rotates relative to the trammels 7 from which the seat is suspended. This permits the seat always to remain in an upright position through gravity forces, regardless of the fact that the unit is negotiating an obstruction. Thus when the wheel chair is climbing a stairway, as seen in FIG. 10, the trucks push the front portion of the movable support frame upwardly so that the support frame pivots in a counterclockwise direction. Despite this movement of the frame, however, the chair unit remains upright because of the rotation permitted by the rollers 18, 19, 20 and 21 which connect the trammels to the upper portions 14 of the movable support frame. Any possible tendency to tip is precluded by the guide pins 2e in the slots 25 which stabilize the chair from a point below the curved tracks 14. Of course, tipping of the chair unit is prevented also by the location of the pivotal connection at pin 10 between the chair assembly and the trammels along the line 11 that intersects the center of gravity of the unit.

Movement down the stairway is accomplished somewhat in the same manner as climbing the stairs. Again the pivotal mounting of the trucks on the movable support frame permits them to go down the risers of the stairs and onto the treads of the succeeding steps downward. As before, regardless of the fact that the wheel chair is entirely located on the stairway, there are always several wheels positioned on the horizontal treads of the stairs. Thus, the equilibrium is maintained, and there is no tendency for the wheel chair to run away down the stairs. Of course, as the unit descends the stairway, the movable support frame 2 rotates in a clockwise direction relative to the trammels 7 and the chair unit 1. The unit will not tip and the chair and the occupant remain in the upright position when going down the stairs as well as climbing up.

Naturally in negotiating stairs or other obstructions, the automatically operated brake assures complete safety of the unit. Thus even if the occupant should become fatigued or wish to stop the unit for any reason while at a mid point on the stairway, merely by releasing the hand wheels 68 the brake automatically is applied and the chair cannot move. The use of a reliable chain drive assures that the wheels will be locked and the chance of failure is negligible. Furthermore, by having a brake on either side of the chair, even in the unlikely event of malfunction of one portion of the braking system, the other will be adequate to hold the Wheel chair in position.

Steering of the wheel chair of this invention is similar to that of any caterpillar type vehicle and is accomplished very simply by appropriate manipulation of the hand wheels 68. Rotation of only one of the hand wheels will cause the unit to pivot around, or it may be turned efficiently by rotation of one hand wheel 68 forwardly and the other in reverse.

It can be seen, therefore, that through the provision of a relatively easily constructed and manufactured unit, a wheel chair is obtained that is capable of performing entirely unlike one of conventional design. The unit is versatile in its use and relatively light in weight. The provision of the drive means and the running gear on either side of the chair unit permit the wheel chair to be folded flat as with the practice for conventional designs. Thus the advantages of ordinary wheel chairs are retained, and the wheel chair unit of this invention is readily stored or transported.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

I claim:

1. A wheel chair comprising a seat unit; a support frame; a suspension means pivotally supporting said seat unit and engaging said support frame for support thereby, said support frame being rotatable relative said suspension means; a drive train supporting said support frame, said drive train including a plurality of trucks each of which is pivotally connected to said support frame, each of said trucks having wheel means; and means for driving said wheel means.

2. A wheel chair comprising a seat structure; a support unit, said support unit having an arcuate guide means defining a curvilinear path; means pivotally engaging said seat structure and further engaging said arcuate guide means of said support unit for movement in said curvilinear path; a running gear, said running gear including a plurality of trucks, each of said trucks being pivotally connected to said support unit and including wheel means; and means for driving said wheel means.

3. A device as recited in claim 2 including in addition brake means for precluding rotation of said wheel means except by said driving means.

4. A wheel chair comprising a seat unit; a pair of side members located one on either side of said seat unit, one end of each of said side members being pivotally connected to said seat unit; a support unit, said support unit including a pair of arcuate members slidably engaging said side members; a drive train, said drive train including a plurality of longitudinally arranged trucks on either side of said seat unit so as to provide a pair of rear trucks and additional trucks extending forwardly of said rear trucks, each of said trucks having wheel means, fixed pivot means connecting each of said rear trucks to said support means, and link means connecting each of said additional trucks to said support unit; and drive means for effecting equal and simultaneous rotation of said wheel means.

5. A device as recited in claim 4 in which said drive means comprises a plurality of roller chains and a plurality of sprockets rotatably fixed to said wheel means whereby said roller chains drivingly interconnect said wheel means.

6. A device as recited in claim 4 in which for said plurality of longitudinally arranged trucks said drive train includes four trucks on either side of said seat unit, each of said trucks including two longitudinally aligned wheels, said link means for the forward one of said trucks on either side including a single link extending upwardly to said support unit, said link means for the center two of said trucks including a single link extending upwardly from each of said center two of said trucks, and a beam pivotally connected at its center to said support unit and pivotally engaging said last mentioned links at its opposite distal ends.

7. A device as recited in claim 4 in which said drive means includes a rotatable shaft, a drive sprocket rotatable with said shaft, sprocket means on said wheel means, and a chain interconnecting said drive sprocket and said sprocket means on said wheel means whereby rotation of said shaft through said chain causes rotation of said wheel means.

8. A device as recited in claim 7 in which said chain from said drive sprocket rotatably connects to the rearmost of the wheels of said trucks.

9. A device as recited in claim 7 including in addition a brake interposed between said rotatable shaft and said drive sprocket, said brake including means for automatically locking said drive sprocket in the absence of a driving torque on said rotatable shaft, and automatically unlocking said drive sprocket when such a driving torque is present.

10. A device as recited in claim 9 in which said rotatable shaft includes at least one receptacle spaced outwardly from the axis thereof, said brake including a ball in said receptacle and projecting outwardly therefrom, said drive sprocket being axially movable relative to said receptacle and including an aperture engaging outer portions of said ball, an annular friction member arranged adjacent said drive sprocket, and a spring biasing said sprocket toward said friction member, whereby upon exertion of a driving torque on said rotatable shaft said balls urge said sprocket axially away from said friction member for thereby releasing said brake and in the absence of said driving torque said spring urges said sprocket against said friction member.

11. A wheel chair comprising a seat unit, suspension means for said seat unit, said suspension means pivotally connecting to said seat unit along a vertical line substantially falling upon the center of gravity of said seat unit when said seat unit is occupied; a support unit, said support unit including guide means defining a curved path convex upwardly and aligned longitudinally of said chair unit, said suspension means including means engaging said guide means for support by said support unit and movement relative thereto along said fixed path; a plurality of truck means, each of said truck means including wheel means, and means pivotally connecting said truck means to said support unit; and drive means for effecting rotation of said wheel means.

12. A device as recited in claim 11 in which for each of said truck means said wheel means includes a duality of longitudinally aligned wheels rotatably carried thereby, and said drive means includes means for equally and simultaneously rotating said Wheels.

13. A device as recited in claim 11 in which said trucks means includes on either side of said seat unit a rear truck, a front truck and a duality of intermediate trucks, said means pivotally connecting said trucks to said support unit including a fixed pivotal connection on said support unit for said rear trucks, a link pivotally interconnecting said front trucks and said support unit, a link one end of which is pivotally connected to one of said intermediate trucks, another link one end of which is pivotally connected to the other of said trucks, a longitudinally arranged beam pivotally connected to said support unit at a location intermediate its ends, said links connected to said intermediate trucks connecting at their opposite ends to said beam at said ends of said beam.

14. A wheel chair comprising a seat unit, a duality of suspension members, said suspension members being located one on either side of said seat unit and pivotally connected to said seat unit at a point above the center of gravity thereof and in substantial vertical alignment therewith; a duality of support members, said support members being located one on either side of said seat unit, each of said support members including guide means defining a fixed arcuate path convex upwardly and arranged longitudinally of said seat unit, each of said suspension means engaging the adjacent support means at said guide means thereof for movement along said path; a duality of sets of trucks, said sets of trucks being located one on either side of said seat unit, each of said sets including a plurality of longitudinally aligned wheels, each of said trucks being pivotally connected to the adjacent one of said support members, the trucks in each set being pivotally interconnected, each of said trucks including wheel means; and drive means for simultaneously and equally rotating all of said wheel means on either side of said chair unit.

15. A device as recited in claim 14 in which said drive means includes means for selectively applying a torque to said wheel means, and a brake means, said brallc means including means for locking said wheel means against rotation when no torque is being applied by said torque applying means, and means for unlocking said wheel means when a torque is applied by said torque applying means.

16. A wheel chair comprising a seat unit; a pair of suspension members located one on either side of said seat unit, said suspension members pivotally connecting to said seat unit along a transverse axis substantially vertically aligned with the center of gravity of said seat unit when said seat unit is occupied; a pair of support members located one on either side of said seat unit, each support member including an arcuate track portion defining a fixed curvilinear path convex upwardly and longitudinally arranged with respect to said seat unit, each of said suspension members including roller means heneath said pivotal connection engaging said track for supporting said suspension members on said track with freedom for movement along said fixed curvilinear path; a pair of drive trains located one on either side of said seat unit beneath the adjacent support member, each of said drive trains including four longitudinally aligned trucks, each of said trucks having a duality of longitudinally aligned ground-engaging wheels, the rearmost of said trucks of each train being pivotally connected to the rearward portion of said support member; a link pivotally connecting the forward one of said trucks of each train to said support member at the forward portion of said support member; a link extending upwardly from each of the trucks intermediate said forward and rearward truck; a longitudinally extending beam for each train pivotally connected to the adjacent support member about a transverse axis disposed beneath said curvilinear path, said links for said intermediate trucks of each train being connected to said beam on opposite sides of said transverse axis, and power input means connected to the wheels of each of said drive trains for providing equal and simultaneous rotation of all the wheels in each drive train.

17. A device as recited in claim 16 including an automatic brake connected to said wheels, said brake including means for locking said wheels against rotation other than by said power input means.

18. A device as recited in claim 16 in which said means for rotating said wheels includes a receptacle member rotatable about a circumference around an axis, a ball in said receptacle rotatable relative thereto and projecting therefrom, sprocket means adjacent said receptacle and axially movable relatively thereto, said sprocket means having an aperture therein adapted to receive and engage portions of said ball, said aperture being of smaller diameter than the diameter of said ball, resilient means biasing said sprocket means toward said receptacle, a friction member engaged by said sprocket means when said sprocket means is in said position for precluding rotation of said sprocket means, whereby rotation of said receptacle relative to said sprocket means causes said ball to exert an axial force on said sprocket means urging said sprocket means away from said receptacle to a position remote from said friction member, and an abutment on said sprocket means engageable by said receptacle upon such relative rotation of said receptacle for thereby providing a driving connection between said receptacle and said sprocket means.

19. A device as recited in claim 18 including in addition manually operable screw thread means engageable with said sprocket means for moving said sprocket means relative to said receptacle to said remote position and holding the sprocket means in said remote position for thereby precluding said resilient means from biasing said sprocket means against said friction member.

20. A wheel chair comprising a seat unit, support means for said seat unit, said support means including a first portion pivotally connected to said seat unit, and a second portion having a guide means defining a curvilinear path, said first portion engaging said guide means and being movable in said curvilinear path, a plurality of wheel means supporting said second portion, and drive means for rotating said wheel means.

References Cited in the file of this patent UNITED STATES PATENTS 882,248 Haas Mar. 17, 1908 1,739,260 Roe Dec. 10, 1929 2,436,619 Swindell Feb. 24, 1948 2,742,973 Johannesen Apr. 24, 1956 2,787,472 Foggiano et al. Apr. 2, 1957 FOREIGN PATENTS 1,059,735 France Nov. 10, 1953 

